Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$240.60	9.284%	$262.9373	$262.94	$262.95	$262.90
Purchase #2	$77.54	5.691%	$81.9528	$81.95	$81.95	$82.00
Purchase #3	$187.60	10.157%	$206.6545	$206.65	$206.65	$206.70
Purchase #4	$49.43	7.275%	$53.026	$53.03	$53.05	$53.00
Purchase #5	$99.97	11.835%	$111.8014	$111.80	$111.80	$111.80
Purchase #6	$34.39	10.151%	$37.8809	$37.88	$37.90	$37.90
Purchase #7	$119.53	9.528%	$130.9188	$130.92	$130.90	$130.90
7 purchase totals =	$809.06		$885.1717	$885.17	$885.20	$885.20